Chapter 54: Review Of The Immune System Flashcards
2 types of immune responses
Natural immunity and acquired immunity
Natural immunity (innate)
At location
Respond immediately, generalized
Inflammation response and recruiting cells that phagocytize pathogens
Chemical barriers
HCl (stomach), Lysosome (sweat, tears), lactic acid (vagina)
Physical barriers
Skin, mucosa (resp. GI, GU)
Initial immune response
Macrophages recognize pathogen and activate innate system
Dendritic cells pick up antigens and track down T and B cells, activate specific system
Invading pathogen activates the complement system via lectin pathway or alternative pathway
Release cytokines (signalling proteins) to receive help and alert infection -> inflammation. Cytokines recruit more macrophages, monocytes, neutrophils. Inflammation also causes vasodilation, increase vas permeability, mast cell degranulation, activation of clotting system, and activation of kinin system. Inflammation also causes neutrophils and macrophages to release more cytokines called interleukins. This is known was the acute phase response -> systemic inflammatory response -> release more cytokines -> interleukin 1 to the brain to signal fever, decrease appetite, and lethargy. Interleukin 6 -> liver to produce acute phase proteins (opsonins). IL-8 recruits and activates more neutrophils. IL-2 and IL-12 activate NK cells. TNF-alpha is release and dose all of these effects by itself
Phagocytosis
destroy pathogens after they are recognized. Wrap cell membrane around pathogen and absorb them in cell. Destroy pathogen using enzymes and turning them into harmless waste products
Opsonins
complex molecules that attach to pathogens and make it easier for macrophages and neutrophils to recognize and phagocytize that pathogen. Ex. CRP produced by liver by IL-6. measure CRP in pt to see how much inflammation is in the body. Great indicator of level of infection.
Specific acquired immunity
Away from infection
Specialized, takes longer to respond
Cell-mediated
T cells
Antibody-mediated: Humoral
B cells
T and B cells are lymphocytes and free to roam in blood and lymphatic system. Spend most time in lymph node and mucosa associated lymphoid tissue
Complement system
Complement system works alongside the innate and specific immune system
Helps them destroy pathogens
Complement proteins C1-C9
Once system is activated, proteins activate each other thru complement cascade
Results in opsonins, inflammation, destroy pathogens
Triggered directly by pathogens (lectin and alt. pathway) and classical (AB-AG complexes)
B lymphocytes
Make Ab
B cells have AB on cell membrane that are specific to single antigen
Plasma cells are B cells that have differentiated and become AB producing cells
Cytolytic T lymphocytes
Cytolytic T cells, CD8 cells
Do not produce antibodies
Attack and kill target cells directly
Each t cell has t cell receptors that are specific to single antigen
Dendritic cells
Dentrictic cells are messengers that pick up antigen and display them on cell surface (HLA class 2 moelcules) and bring them into lymph system. When a b or t cell recognize pathogen, they become activated. Start the specific immune response.
Helper t lymphocytes
Helper T cells, CD4 cells
Antibody production by B cells
Required for an effective immune response
Activation of cytolytic T cells
Promote type IV sensitivity reactions, also known as delayed-type hypersensitivity (DTH)
Specific immune response
Present to CD4 t cell then proliferation to TH cells -> release cytokines to present molecule on HLA class 1 molecule so they can be recognized by CD8 t cell -> differ into cytotoxic t cell
TH cells also release cytokines for C B cells -> plasma cells –> AB and memory B cells for immune memory
TH cells also travel to site of infection to release cytokines to recruit macrophages and macrophages to site of infection -> phagocytosis and inflammation
TC cells destroy virally infected cell by attaching themselves to HLA class 1 molecule antigen 2 ways -> 1. Granule exocytosis. Spray infected cell with enzymes -> cell lysis. 2. FAS molecule activation. “Self destruct switch” once activated, it causes cell to undergo apoptosis
Plasma cells are B cells that have differentiated and become AB producing cells
Macrophages
Begin in bone marrow, enter blood as monocytes, and infiltrate tissues, where they evolve into macrophages
Principal scavengers of the body
Recognize pathogens via pathogen associated molecular patterns using receptors (toll-like receptors)
Specific acquired immunity
Activation of T cells
Final mediators of DTH
Phagocytize cells tagged with antibodies
Also play key roles in natural immunity and inflammation
Mast cells and basophils
Mediate immediate hypersensitivity reactions
Release histamine, heparin, and other compounds that cause s/sx of immediate hypersensitivity
Mast cells are located in skin and others soft tissues
Basophils are in the blood
Neutrophils
Polymorphonuclear leukocytes (PMNs)
Phagocytize bacteria and other foreign particles
Eosinophils
Attack and destroy foreign particles that have been coated with antibodies of the immunoglobulin (Ig) E class
Antibodies
Alternative names
Immunoglobulins
Gamma globulins
Family of structurally related glycoproteins
Mediate humoral immunity
Recognize and bind with specific antigens
Produced by B lymphocytes
Five classes of antibodies:
IgA, IgD, IgE, IgG, and IgM
Y shaped
Top is variable region that matches different Ag
Bottom is fixed shape and recognized by many cells of immune system
Help immune system:
Attach to toxins (Ag) and neutralize them
Attach to receptors of viruses and bacteria and prevent them from carrying out their function
Agglutination
Opsonins that are highly specific to invading pathogen
Antigens
Molecules that induce specific immune responses
May trigger production of antibodies or cytotoxic T cells, or both
Antibodies recognize and bind selected small portions of the antigen
More than one antibody can bind to the antigen
Characteristic Features of the Specific Immune Response
Specificity
Immune responses are triggered by specific antigens
Diversity
Millions of different antigenic determinants
Memory
Exposure to an antigen affects the immune system such that reexposure produces a faster, greater, and more prolonged response
Time limitation
Immune responses only last while there is stimulus
Selectivity for antigens of nonself origin
Targets only foreign antigens (normal conditions)
Phases of immune response
Recognition phase
Antigen recognition by B cells and T cells
Activation phase
Proliferation
Differentiation of activated lymphocytes
Effector phase
Elimination of antigen
Major Histocompatibility Complex Molecules
Group of genes that codes for major histocompatibility complex (MHC) molecules
MHC molecules become expressed on the surface of all cells
Play a key role in the activation of helper and cytotoxic T lymphocytes
Guide cytotoxic T lymphocytes toward target cells
Provide the basis for distinguishing between self and nonself
Class I MHC molecules
Found on virtually all cells except erythrocytes
Located on the surface of antigen-presenting cells (APCs)
Help initiate immune responses by “presenting” antigen to cytotoxic T cells
Class II MHC molecules
Found primarily on B cells and APCs (macrophages and dendritic cells)
Located on the surface of APCs
Help initiate immune responses by presenting antigen to helper T cells
Cytokine
Any mediator molecule (other than an antibody) released by any immune system cell
Lymphokine
Cytokine released by a lymphocyte
Monokine
Cytokine released by a mononuclear phagocyte (monocyte or macrophage)
Antibody-Mediated (Humoral) Immunity
Production of antibodies
Interaction of three types of cells:
B cells
Make antibodies
Helper T cells (CD4 cells)
Stimulate B cells
Antigen-presenting cells (macrophage or dendritic)
Activate CD4 cells
Antibody effector mechanisms
Opsonization of bacteria
Activation of the complement system
Neutralization of viruses and bacterial toxins
Type IV Hypersensitivity (Cell-Mediated Immunity)
Delayed-type hypersensitivity
Activation of helper T cells
Activation of macrophages
Cytolytic T lymphocytes (CTLs, CD8 cells)
Activation of cytolytic T cells
Recognition of virally infected target cells
Mechanism of cell kill
Binding of a CTL to its target cell
Release of mediators that kill the target
Cause target-cell lysis
